Effect of melittin on potassium currents and action potential in ventricular myocytes of guinea pig

AIM: To examine the effects of melittin (Mel), the major component of bee venom, on delayed rectifier K⁺ current (I(k)), inward rectifier K⁺ current (I(k1)) and action potential (AP) in guinea pig ventricular myocytes. METHODS: I(k), I(k1), and AP were recorded using the whole-cell patch-clamp technique. RESULTS: The action potential duration (APD) was shortened by Mel in a concentration-dependent manner. Mel 0.05, 0.1, 0.2 μmol·L^-1 shortened APD₅₀ from (520 ± 55) to (459 ± 91) (n=5, P>0.05), (385±102) (n=5, P< 0.01), and (281±81) ms (n=5, P<0.01), respectively; and APD₉₀ from (613±96) to (536±93) (n= 5, P>0.05), (467±96)ms (n=5, P<0.01), and (354±95) ms (n =5, P <0.01), respectively. Mel increased the amplitude of I(k) also in a concentration-dependent manner. Mel 0.05, 0.1, 0.2 μmol · L^-1 increased I(k) from (295 ± 109) to (371 ± 142) (n = 5, P <0.05), (467±180) (n=5, P<0.05), (552±248) pA (n = 5, P < 0.05), respectively at testing potential of + 40 mV. But no significant effect of Mel on I(k1) was observed at these concentrations. CONCLUSION: Mel significantly increased I(k) in a concentration-dependent manner which contributed to shortening of APD.